The present invention is directed to an identification device, preferably a wristband or an adhesive label, comprising a direct thermal printable surface having antimicrobial properties. Specifically, the identification device is configured for receiving identification information by means of a direct thermal printer and having antimicrobial properties without the use of a protective layer or overcoat on top of the direct thermal layer.
Direct thermal printable media is used in printers and in other applications requiring permanent imaging such as wristbands, tags, labels and other identification media. In contrast to printing technologies that involve the transfer of ink from one location to another, direct thermal printing uses a special printable media that incorporates a color developing mechanism. Images are formed by exposing the color developing mechanism to concentrations of heat that produce localized chemical reactions involving a change of color (usually light to dark). The color developing mechanism is provided by a thermosensitive imaging material containing heat reactive chemicals such as leuco dyes or metallic salts.
Since direct thermal printing only involves the transfer of heat, printing of direct thermal media is simple and clean. Other advantages include low cost, low noise, and high speed. The thermosensitive imaging material is typically applied as a layer on top of a substrate surface. Printing takes place by exposing the coating to a pattern of heat conducted from a thermal print head located adjacent to the substrate surface containing the coating of thermosensitive imaging material.
There has been a great deal of attention in recent years given to the hazards of bacterial contamination from potential everyday exposure. Noteworthy examples of such concern include the fatal consequences of food poisoning due to certain strains of Eschericia coli being found within undercooked beef in fast food restaurants; Salmonella contamination causing sicknesses from undercooked and unwashed poultry food products; and illnesses and skin infections attributed to Staphylococcus aureus, yeast, and other unicellular organisms. With such an increased consumer interest in this area, manufacturers have begun introducing antimicrobial agents within various products and articles.
Silver-containing inorganic microbiocides have recently been developed and utilized as antimicrobial agents on and within a plethora of different substrates and surfaces. In particular, such microbiocides have been adapted for incorporation within plastic compositions and fibers in order to provide household and consumer products which inherently exhibit antimicrobial characteristics. Although such silver-based agents provide suitable antimicrobial properties within thermoplastic articles, and other types of articles, there are certain limitations as to the potential antimicrobial efficacy of such thermoplastic articles. Such limitations are apparently due to relatively low amounts of surface-available silver within and/or on such thermoplastic articles. Without intending to be bound to any specific scientific theory, it is believed that such low surface-available amounts of silver are the result of the inability of a sufficient amount of the integrated silver compounds to migrate to the thermoplastic surface. Such a result is observed for standard thermoplastics comprising silver-containing antimicrobials. Thus, there exists a need to provide efficacious amounts of silver-containing antimicrobial agents within thermoplastic compositions that exhibit such heretofore unattainable high levels of surface-available silver compounds, thereby providing more effective antimicrobial activity, among other potential desirable characteristics as a result thereof.
Past plastic compositions and articles comprising silver-containing antimicrobial agents include U.S. Pat. No. 5,405,644 to Ohsumi et al., which includes the addition of certain triazoles; U.S. Pat. No. 4,938,955 to Niira, et al. (also including benzotriazole stabilizers); U.S. Pat. No. 5,750,609 to Nosu et al., which discloses an ultraviolet protective agent for incorporation within a variety of compositions, such as films, fibers, cosmetics, and the like, comprising a zinc-based hydrotalcite which acts solely as an ultraviolet absorber. However, these particular methods and plastics have proven to be costly (with the high expense of benzotriazoles initially), particularly since relatively high concentrations of the expensive stabilizing compounds are required, and do not provide any appreciable increase of available silver on the surface of such articles. Also, as these stabilizers are not thermally stable, they introduce additional processing complications. As such, there is no teaching or fair suggestion within the prior art which pertains to the needed improvement in increasing the amounts of surface-available silver compounds on target thermoplastics.
Another such prior art product includes the Zebra antimicrobial wristband. The Zebra product has the antimicrobial material within a varnish applied on top of the direct thermal material in a secondary process as disclosed in U.S. Patent Publication No. 2006/0248767. There are several disadvantages to using an antimicrobial varnish as in the Zebra product, including: inconsistent printing due to variation in the varnish thickness, discoloration of the varnish when exposed to UV light, shorter print head life, build-up of the varnish on printer rollers, and relatively lower speeds/higher heat energy requirement for the printing process.
Accordingly, there is a need for an identification device configured for receiving identifying indicia by means of a direct thermal printer and that exhibits antimicrobial properties without the associated disadvantages of an overcoat or varnish. The present invention fulfills these needs and provides other related advantages.